1. Field of the Invention
The present invention relates to synthetic resin composites having singular tribological properties for bearings, and more particularly to bearings such as slide bearings molded therefrom.
2. Description of the Related Art
A bearing is defined as a means of positioning one part with respect to another in such a way that relative motion is possible. This relative motion and its type are dictated by how the bearing will be used. Bearings are designed by determining the mechanical functions in which the bearings must perform, the bearing's life and reliability requirements, and the bearing's ambient conditions, including temperature, corrosive atmospheres, and vibration.
One type of bearings is a slide bearing, in which the bearing elements are usually separated by a film of lubricant (e.g., oil or grease) and in which a sliding motion is the predominant element. Another type of bearing is a rolling-element bearing.
Slide bearings include all varieties of bearings in which the primary motion is a sliding of one surface over another. A sleeve bearing which is used to position a shaft or movable part in a radial direction is an example of a slide bearing.
Rolling-element bearings include ball bearings, roller bearings, and needle bearings. Both ball and roller bearings are made and designed to carry either radial or thrust loads or both. Needle bearings, in general, are restricted to radial loads.
Slide bearings, in general, require relatively large amounts of lubricant (e.g., oil) in order to maintain a lubricant film between the surfaces. Lubricants vary widely from fluids of all types, including water, oil, soaps, greases and air, to solid lubricants such as graphite and molybdenum disulfide. Unless the loads are very low, the pressure that is generated in the lubricant film to support the load also drives lubricant out of the bearing. Lubricant lost in this manner must be continuously replenished.
Synthetic resins, such as polyamides, polyesters, and polyolefins, e.g., polypropylene, polyethylene and polyacetals are known to be used in the manufacture of sliding members, such as slide bearings. Polyamides, particularly nylon 66, are preferred for their mechanical, chemical, and physical properties, which are especially useful for slide bearings. See, for example, Official Publication of Toku Kai Hei 5-32797.
RBC (RB ceramics) and CRBC (CRB ceramics) are also known as moldable carbon materials. See, for example, Kazuo Hokkirigawa, Kino Zairyo “Functional Materials”, Vol. 17, No. 5, pp. 24–28 (May 1997).
Lubricant resin composites are also known. These composites are prepared by adding from 5 to 40 parts by volume of a solid lubricant to 100 parts by volume of a fiber-reinforced resin made of from 60 to 95 volume percent synthetic resin and from 40 to 5 volume percent carbon fibers. See, for example, Official Publication of Toku Kai Hei 7-268126.